Indexing device

ABSTRACT

An indexing device has a first crown gear arranged on a first annular body secured to an indexing table, a second crown gear arranged on a second annular body secured to a housing, and a third crown gear arranged on an axially movable third annular body. The third crown gear can be taken out of and into engagement with the other annular crown gears by a hydraulically operable lifting and lowering device. A radial bearing supports the indexing table rotatably on the housing. The lifting device has one lifting piston which is fitted to move axially inside the housing and operates with the third crown gear. The lowering device can be hydraulically operated and has at least one hollow chamber which can be filled with fluid and is bounded on the one hand by the third crown gear. A fourth annular body engaged in an annular groove in the third annular body forms a guide for moving the third crown gear. This indexing device is compact, economical to produce, easy to fit and maintain and reliable in operation.

FIELD OF THE INVENTION

The present invention relates to an indexing device with a first crowngear arranged on a first annular body connected with an indexing table,with a second crown gear arranged on a second annular body connectedwith a stationary housing, and with a third crown gear arranged on anaxially slidable third annular body. The third crown gear can be broughtinto and out of engagement with the first and second annular crown gearsby means of a hydraulically operable lifting and lowering device. Aradial bearing supports the indexing table rotatably on the housing. Thelifting device incorporates at least one lifting piston, which issupported axially movably within the housing and cooperates with thethird annular body.

BACKGROUND OF THE INVENTION

In an indexing device, such as disclosed in Japan A-2 041 850, thefourth annular body exclusively along its exterior periphery forms aguide for the longitudinally slidable third annular body. The knownlifting and lowering device used at this point has two hollow chambersseparated from one another by the fourth annular body and filledalternately with liquid. In the case of this known arrangement,hydraulically controllable separate lifting pistons are usedexclusively. Because of such pistons, the indexing device is of largestructural dimensions. Also, this arrangement provides non-optimum fluxof force. With the lifting of the third annular body for the purposes ofengagement and mating of the crown gears with one another, a favorablemoment of force arises as a result of the offset of the third annularbody projecting out further than the crown gears.

An indexing device is disclosed in German 26 28 677 C2 wherein theradial bearing of the indexing table is arranged between the two coaxialfirst and second annular bodies. Each annular body is provided withrespectively first and second crown gears. Compared with the devicesknown until this time, the rotation factor error of this indexing tableis decreased. Thus, the annular bodies supporting the crown gears inturn can be configured as supporting bodies and are manufactured withgreat precision on their bearing surfaces. Precise manufacturing ofthese rings is also required with regard to the crown gears provided onthese annular bodies. The parts required for precision of rotation areto be accommodated in a narrow construction space. Since the annularbodies with their crown gears are manufactured precisely, the precisionof the relevant parts and the rotation precision of the indexing tableare, for the most part, guaranteed.

With the known arrangement, in order to slide the axially slidable thirdannular body axially upwardly and consequently to disengage its thirdcrown gear from the two other crown gears of the other annular body,lifting pistons of a hydraulically operable lifting device are arrangedin the housing of the indexing device around the periphery atpredeterminable defined distances from one another. The lifting pistonsundertake the decoupling or disconnecting process from the center,controlled by an auxiliary attachment. For the lowering process andconsequently for bringing the crown gears, which in this case are called"Hirth gearings", into engagement with one another, the lifting pistonsof the lifting device are made pressureless. A disk spring set engageson the relevant lifting piston and takes over the axial resettingmovement. With the force of the spring set, the engagement of the thirdcrown gear of the third annular body with the other crown gears issecured for further operation of the switching device.

This type of structural arrangement requires a plurality of liftingpistons and disk spring sets in the housing. The hydraulic control,including the necessary casing or lining, is costly. Furthermore, thelifting and lowering device in the known indexing devices isincorporated in the housing. Raising of the indexing table from thedevice by means of a lifting tool or the like for maintenance andassembly procedures is achievable only with great difficulty, which alsoincreases the concomitant costs.

An alternative type of indexing table device, disclosed in German 21 37698 C3, has a lowering device which is hydraulically operable, and, forthis purpose, has hollow chambers which can be filled with liquid. Thehollow chambers are arranged at the end of the third annular bodyincorporating the third crown gear, and are controlled and filled withliquid alternately to bring the third crown gear in or out of engagementwith the two other crown gears for fastening and release of the indexingtable. Consequently, with this known indexing device, a hydraulicallycontrollable separate lifting piston is used exclusively. For thelifting of the third annular body with the third crown gear, the liquidpressure on the third annular body works on this body eccentrically andin addition to the crown gears. Also, with lowering of the third annularbody, a nonuniform liquid pressure arises and works on it. This leads tolower the maximum power flux. The "backfilling" arising as a result ofthe nonuniform introduction of force between the annular bodies withtheir crown gears and tolerance compensation thus becoming required isattained by dividing the third annular body into two partial rings. Thepartial rings in turn are provided with a third crown gear and areconnected with one another through an elastically flexible intermediateelement. Because this intermediate element is subjected to corrosion orattrition, the rigidity required for reliable operation of the liftingand lowering device is lost. Also, the required mating precision of thecrown gears fitting into one another for securing the indexing device isnot guaranteed. Therefore, the lifting and lowering device of this knownindexing device is of complicated construction and is accessible onlywith difficulty for maintenance and assembly.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide an indexing device whichis of small construction, of lower manufacturing and assembly andmaintenance cost and is secure in operation.

The foregoing objects are basically obtained by an indexing device,comprising a stationary housing and an indexing table rotatablysupported on the stationary housing by a radial bearing. A first crowngear is arranged on a first annular body connected to the indexingtable. A second crown gear is arranged on a second annular bodyconnected to the stationary housing. A third crown gear is arranged onan axially slidable third annular body. The third annular body ismovable between a first position in which the third crown gear engagesthe first and second crown gears and a second position in which thethird crown gear is disengaged from the first and second crown gears. Ahydraulically operable lifting and lowering device moves the thirdannular body between the first and second positions. The lifting andlowering device includes a first hollow chamber, and a first liftingpiston. The hollow chamber is defined between the third annular body anda stationary fourth annular body and is fillable with a liquid. Thefourth annular body is engaged in a groove in the third annular body toguide movement of the third annular body between the positions thereof.The lifting piston is axially movably mounted within the housing andcooperates with the third annular body.

The resulting lifting and lowering device needs to be provided along theradial periphery dependent upon the dimensions of the indexing devicenow at only a few points. In addition to having a simplified hydrauliccontrol arrangement for the indexing device, the number of parts isreduced, lowering manufacturing costs and decreasing assembly and repaircosts. The hydraulically operable lifting and lowering device requiresminimal structural space, and consequently, can be arranged in the areaof the bottom of the indexing table, so that the movable parts of thelifting and lowering device remain on top of the housing during thelifting process and are easily accessible from all sides. Since fewerparts are in use, which also work essentially without wear, compared tothe solutions known until this time in this are of technology, theoverall security of operation is increased.

As a result of the center guiding of the third annular body along thefourth annular body, a very rigid construction is guaranteed withoptimum flux of force. The central force introduced in the middle bymeans of the liquid pressure, with lowering of the third annular body,uniformly effects the crown gears in engagement with one another. Therequired tolerances are obtained without use of flexible intermediatemembers, which contributes to the operational security of the indexingdevice according to the present invention. As a result of the relevantlifting piston, optimum introduction of force can likewise be centeredand the disconnection or decoupling step of the crown gears can likewisebe attained.

In the case of one preferred embodiment of the indexing device accordingto the present invention, this optimal introduction of force is stillfurther favored in that the three crown gears are covered and sealed offby the third annular body and are flush with the third annular body. Theliquid flow produced in the hollow chamber, as well as the pistonpressure of the lifting piston, are exerted centrally between the threecrown gears extending on these bodies.

In another preferred embodiment of the indexing device according to thepresent invention, to produce cooperation of the lifting piston with thethird annular body, an operating member controlling the lifting pistonpenetrates the second annular body to engage the third annular body. Atight mechanical connection between the operating part and the thirdannular body is avoided. This contributes to the ease of assembly andservice, and at the same time, guarantees effective lifting of the thirdannular body by means of the lifting piston.

In another preferred embodiment of the indexing device according to thepresent invention, the fourth annular body is tightly connected with thehousing around the assembly by a plurality of separator boltsdistributed around its exterior periphery. Each separator bolt is atleast partially surrounded by the third annular body and is containedtherein. Because of these separator bolts, which are tightly connectedwith the housing, a secure fixing of the annular body in the radialnotch in the indexing table is realized by their fitting in the radialcutouts in the indexing table. Thereby, a rigid guide for the thirdannular body is attained, so that the crown gears are defined in theirdimensions and placement, and can be brought into engagement with oneanother without play at the interface.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the annexed drawings, disclose a preferredembodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings which form a part of this disclosure:

FIG. 1 is a side elevational view in section of an indexing deviceaccording to the present invention;

FIG. 2 is another side elevational view in section of the indexingdevice of FIG. 1; and

FIG. 3 is a further side elevational view in section of the indexingdevice of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first annular body 14 is fastened to an annular projection 10 inFIG. 1. Projection 10 extends axially from an indexing table 12, so thatannular body 14 engages like a lamina on annular projection 10. Screws16 are provided for the required fastening. Pins (not shown) serve forthe positioning of these parts relative to one another. First annularbody 14 supports a first crown gear 18 on its top in the area of itsinside edge. Coaxial to first annular body 14, a second annular body 20is arranged and rests in a cutout of housing 22 of the device. Secondannular body 20 supports a second crown gear 24 on its top. Crown gears18 and 24 lie in one and the same plane, and have identical numbers ofgear teeth. The gear teeth of the two crown gears 18 and 24, in turn,are arranged to lie radially one behind the other. Between the twoannular bodies 14 and 20, rolls 28 are arranged in a cage 26. Togetherwith the cylindrical surfaces of the two annular bodies 14 and 20, theserolls 28 form the radial mounting for the indexing table 12.

Above the two annular bodies 14 and 20, a third annular body 30 isarranged. The side of the third annular body turned toward the twoannular bodies 14 and 20 supports a third crown gear 32 with twoassociated gear trains configured to associate with the two crown gears18 and 24. Annular body 14 is mounted on a flat bearing 34 in housing22. It is secured against lifting from its bearing 34 by retaining ring36, which is fastened to housing 22 and laps over the exterior edge ofannular body 14. A face gear 38 is fastened to the bottom of firstannular body 14 in the area of its exterior edge. Face gear 38 mateswith a worm gear 40 driven by a motor (not shown) on both sides. Theworm gear is mounted rotatably in housing 22.

Bearing 34 can incorporate a annular lubricating groove (not shown).Another annular lubricating groove (not shown) can be integrated intoretaining ring 36 on its part overlapping annular body 14. Furthermore,gaskets can be provided between indexing table 12 on the one hand andretaining ring 36 or housing 22 on the other hand. Third annular body 30with its third crown gear 32 can be brought out of or into engagementwith the other annular crown gears by means of the lifting and loweringdevice indicated in its entirety in FIG. 2 as 44. Third annular body 30is arranged in a radial cutout 50 in indexing table 12 and has a hollowchamber 46. A fourth annular body 54 is mounted within and is encircledby third annular body 30 (FIG. 1), and is tightly or fixedly connectedwith housing 22 by means of screw 52. In this manner, fourth annularbody 54 has gaskets 56 along its interior and exterior periphery. Thegaskets are in sealed engagement with the side walls of a surroundingannular groove 57 of third annular body 30. Fourth annular body 54, asshown particularly in FIG. 1, is connected securely by severalcylindrical separator bolts 58, distributed along its closed exteriorperiphery and having screws 52 passing through them, with housing 22.Fourth annular body 54 and the relevant separator bolt 58 are at leastpartially surrounded by third annular body 30 and are held in thismember.

Third annular body 30 is guided axially movably along the separator bolt58 along another interior guide 56. In each movement setting of thirdannular body 30, gasket 60 of separator bolt 58 engages to provide theconnection of that screw 52, which holds fourth annular body 54 at somedistance from housing 22. Connected with this housing 22, screw 52penetrates the relevant associated cylindrical separator bolt 58, with atapering extension penetrating second annular body 20. Third annularbody 30, which becomes larger in its interior breadth in steps upward,according to the representation of FIG. 1, and together with annularbody 54 and separator bolt 58, surrounds the hollow space 46. Hollowspace 46 forms a sort of annular passage and is connected to a hydraulicfeed and discharge conduit 68 (FIG. 3). Hollow space 46 passes both infront of and behind the penetration area of that separator bolt 58.

A liquid is provided in the first hollow space 46 through liquid feedand discharge conduit 68, as shown in FIG. 3, which, as compared withthe representations of FIGS. 1 and 2, incorporates an identicallongitudinal section through the device circumferentially or angularlyoffset by approximately 20 degrees. Conduit 68 passes through anotherand associated separator bolt 58 and opens at its free end into hollowspace 46. With smaller indexing devices, a lifting and lowering device44 with a liquid feed and discharge conduit will usually suffice for thefirst hollow chamber 46. With devices of larger dimensions, a pluralityof conduits driven with hydraulic oil, as well as lifting and loweringdevices, can be present around the periphery of the indexing table. Froma central point outward, there can be only a few structural parts forthe lifting and lowering process.

As shown particularly in FIG. 2, third annular body 30 is presseddownward under the effect of the pressure medium in first hollow chamber46 and locks the two crown gears 18 and 24 in the position of FIG. 2 bymeans of first annular body 14 and second annular body 20 cooperatingwith one another. Release of this locking setting occurs through thirdannular body 30 together with a lifting piston 70. The lifting andlowering device, indicated in its entirety as 44, is guided axiallylongitudinally movably in second annular body 20 and with its widenedflange or pressure surface 77 in a radial cutout 72 in housing 22.Beneath pressure surface 77 is another second hollow chamber 48. Chamber48 is limited by radial cutout 72 and the bottom of lifting piston 70 ina sealed arrangement, and is connected to another feed and dischargeconduit 66 providing hydraulic oil. If first hollow chamber 46 is madepressureless and second hollow chamber 48 is fed a pressurized medium,third annular body 30 is raised with its third crown gear 32 todisengage the respective crown gears from one another, so that indexingtable 12 can be rotated around its center rotary axis. Lifting andlowering device 44 shown in FIG. 2 can be present only once in the caseof smaller indexing devices. Often, in the case of larger devices, thirdannular body 30 can raise and lower as an entirety or in not shownindividual segments arranged uniformly around the radial periphery ofthe device.

Fourth stationary annular body 54 forms the guide 55 along its interiorand exterior periphery for thrusting third annular body 30, and engagesin annular groove 57 of third annular body 30. Furthermore, crown gears18, 24 and 32 are covered by third annular body 30 and are sealed flushwith this. The liquid pressure can be produced in hollow chamber 46 aswell as the piston pressure of lifting piston 70, and has an effectbetween the three crown gears 18, 24 and 32 running thereon. For thecooperating of lifting piston 70 with third annular body 30, anoperating part 71 of lifting piston 70 penetrates second annular body 20and contacts the bottom of third annular body 30. Third annular body 30is provided in this area with a radial cutout 79 so that in transversesection, as shown in FIG. 2, third annular body 30 has the shape of an"H" in the area of the relevant lifting piston 70. Operating part 71 isreduced in diameter as compared with the bottom piston part 73 withpressure surface 77. Piston part 73, which is consequently widened indiameter, has a gasket 80 on the exterior periphery, which seals theother hollow chamber 48 from the environment and the passage fromhousing 22 to indexing table 12.

If crown gears 18, 24 and 32, as shown in FIG. 2, are in engagement withone another, the top of fourth annular body 54 seals flush with the topof third annular body 30. According to the representations in FIGS. 1and 3, the otherwise essentially U-shaped section of third annular body30 allows for another middle-centered longitudinal guiding throughcutouts adapted corresponding to separator bolts 58 in its bottom.

While a particular embodiment has been chosen to illustrate theinvention, it will be understood by those skilled in the art thatvarious changes and modifications can be made therein without departingfrom the scope of the invention as defined in the appended claims.

What is claimed is:
 1. An indexing device, comprising:a stationary housing; an indexing table rotatably supported on said stationary housing by a radial bearing: a first crown gear arranged on a first annular body connected to said indexing table; a second crown gear arranged on a second annular body connected to said stationary housing; a third crown gear arranged on an axially slidable third annular body, said third annular body being movable between a first position in which said third crown gear engages said first and second crown gears and a second position in which said third crown gear is disengaged from said first and second crown gears; and a hydraulically operable lifting and lowering device for moving said third annular body between said first and second positions, said lifting and lowering device including a first hollow chamber and a first lifting piston, said first hollow chamber being defined between said third annular body and a stationary fourth annular body and being fillable with a liquid, said fourth annular body being engaged in a groove in said third annular body to guide movement of said third annular body between said positions thereof, said lifting piston being axially movably mounted within said housing and cooperating with said third annular body.
 2. An indexing device according to claim 1 whereinsaid third annular body is arranged in a radial cutout in said indexing table; and said first and second annular bodies are coaxial with said crown gears arranged thereon being coplanar and having identical numbers of gear teeth, said gear teeth of said first and second crown gears being radially aligned.
 3. An indexing device according to claim 1 whereinsaid lifting piston comprises an operating part which penetrates said second annular body to engage said third annular body.
 4. An indexing device according to claim 1 whereinsaid fourth annular body is securely connected to said housing by separator bolts distributed about an exterior periphery of said housing; and each of said separator bolts is at least partially surrounded and held by said third annular body.
 5. An indexing device according to claim 1 whereinsaid lifting and lowering device comprises a second hollow chamber which can be filled with liquid; whereby alternatively filling and emptying the respective hollow chambers causes said third annular body to move to said first and second positions.
 6. An indexing device according to claim 1 whereinseveral of said lifting pistons are arranged around said third annular body in segments circumferentially spaced from one another.
 7. An indexing device according to claim 1 whereinsaid first, second and third crown gears are covered by said third annular body; and liquid pressure in said hollow chamber and said lifting piston operate on a central portion of said third annular body between said crown gears.
 8. An indexing device according to claim 7 whereinsaid lifting piston comprises an operating part which penetrates said second annular body to engage said third annular body.
 9. An indexing device according to claim 8 whereinsaid lifting and lowering device comprises a second hollow chamber which can be filled with liquid; whereby alternatively filling and emptying the respective hollow chambers causes said third annular body to move to said first and second positions.
 10. An indexing device according to claim 9 whereinsaid lifting piston comprises a piston part of wider diameter than said operating part, said piston part being exposed in said second hollow chamber and forming a pressure surface on which force from liquid in said second hollow chamber is applied. 